Fitossociologia de campos rupestres quartzíticos e ferruginosos no Quadrilátero Ferrífero, Minas Gerais

the floristic composition and phytosociological structure of two areas with quartzitic and ferruginous (itabiritic) campos rupestres in the quadrilátero ferrífero region of minas gerais state were studied. the aim of this research was to determine if geology and geomorphology influence the vegetation of these communities. the campos rupestres in both lithologies were stratified in three kinds of geomorphologic/phytophysionomic habitats: 1. slopes with grasslands; 2. plateaus with grasslands and 3. lower slopes with woody savannas. in each habitat, 10 plots (10x10m) were randomly defined, totaling 60 plots. frequency, dominance and importance value (iv) parameters were calculated for each species. shannon-wiener (h') and pielou (j') indexes were estimated for each habitat. jaccard index and clustering analysis were used to assess the floristic similarity of the different habitats. there were 165 species in the quartzitic and 160 in the ferruginous grasslands. vellozia compacta was the species with the highest iv in both ferruginous grasslands. lagenocarpus rigidus was the species with the highest iv in quartzitic sloped areas, followed by several phanerophytes. echinolaena inflexa was the species with the highest iv in quartzitic plateaus followed by several phanerophytes and many hemicryptophytic species. the woody savannas in ferruginous areas were dominated by e. erythropappus and v. compacta, while in quartzitic areas by echinolaena inflexa, eremanthus erythropappus and many phanerophytic species. woody savannas were more diverse than grasslands. ferruginous campos rupestres exhibited lower diversity (h'=2.92) and equitability (j'=0.58) than quartzitic ones (h'=3.36; j'=0.66). cluster analysis produced groups corresponding to the lithological and geomorphological habitats. the results give evidence that geology and geomorphology influence the floristic composition of campos rupestres.